This invention relates generally to exit tray corrugation in printers or copiers, and more particularly concerns a three stage variable force idler for exit tray corrugation.
As xerographic copiers and printers of all kinds increase in speed, it is increasingly important to provide copy sheet output devices that can reliably stack copy sheet output devices that can reliably stack copy sheet output from such machines. At present, some machines feed copy sheets to stacking trays at such high rates that jams are caused in the trays because preceding sheets do not have time to settle to the bottom of the stacking tray before succeeding sheets are forced into the trays by the transport systems of the machines. Stacking problems occur when the exit rolls send the copy sheet so far up the stacking ramp that the following copy sheet runs into the trail edge of the previous copy sheet before the previous copy sheet has an opportunity to settle down the stacking ramp. Also, the trail edge of preceding copy sheets are sometimes lifted up and out of the stacking tray by the lead edges of incoming sheets because of a small interdocument sheet gap.
The following disclosures may be relevant to various aspects of the present invention and may be briefly summarized as follows:
U.S. Pat. No. 5,280,901 to Smith et al. discloses a sheet feeding and corrugating system, especially for output of image substrate sheets of a reproduction apparatus, wherein the sheets are fed in a normal path through a sheet feeding nip comprising plural spaced sheet feeding rollers. Both feeding and variable corrugation of flimsy or stiff sheets is provided by spherical balls freely mounted in generally vertical ball retainers providing for vertical movement and dual axis rotation against the sheet feeding rollers to define the sheet feeding nip and by additional similar balls (in additional similar ball retainers) intermediately of the feed rollers, which additional balls are unsupported vertically except by bottom-of-travel retainers so that these additional intermediate balls roll gravity-loaded against a sheet being fed through the nip to provide sheet corrugation varying automatically with the stiffness of the sheet, and are freely liftable up to the level of the nip by stiff sheets resisting corrugation. These balls may be readily added to or removed to independently increase or decrease the sheet nip and/or corrugation forces at their respective locations transverse the nip. A sheet side shifting mechanism can laterally offset the sheets in the same nip to eject offset, by moving only the sheet feeding rollers, without resistance from the stationarily mounted balls, all of which roll freely laterally as well in the normal feeding direction.
U.S. Pat. No. 4,789,150 to Plain discloses a sheet stacking apparatus for use with throughput from high speed copiers or printers includes dual independently acting control flaps that provide positive control of sheets being stacked in the apparatus by controlling the trail edges as well as the entire sheets as they are fed into a catch tray.
Xerox Disclosure Journal entitled "Sheet Skewing Systems for Passive Decelerating Eject Rolls" by B. Mandel et al, Vol. 17, No. 3, May/June, 1992, pp. 135-137, discloses non-nip corrugation systems with common size passive decelerating eject rolls that insure proper registration in an up-hill compiling tray by skewing sheets.